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Your guide to lab tests

May 3, 2020 By One Medical
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Updated May 7, 2020.

A regular part of the experience at One Medical may include lab testing. Often, labs are ordered during a visit due to patient concerns, for routine wellness testing, or for ongoing management of chronic medical conditions (such as high blood pressure or diabetes). But what do these labs mean? The results, often filled with a number of abbreviations and unfamiliar terms, can get a bit confusing. This guide will help give you an understanding of what some of the most common laboratory tests are meant to evaluate, what normal results indicate, and why your provider may have suggested it to you.

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Types of Lab Tests

  • COVID-19 (Coronavirus) PCR Testing
  • COVID-19 (Coronavirus) IgG Antibody Testing
  • Cholesterol (Lipid) Panel
  • Hemoglobin A1C and Glucose Tests
  • General Lab Tests
  • Antibody/Immunity Tests
  • Inflammatory/Autoimmune Tests
  • Vitamin Tests
  • Infectious Disease/STI Tests
  • Cultures
  • Hormone Tests

COVID-19 PCR Testing

This test detects the presence of genetic material from the SARS-CoV-2 virus itself, and is the best test to diagnose COVID-19 in symptomatic individuals.

“Detected” result means SARS-CoV-2 genetic material was present.

If you have had symptoms, we recommend you continue self-isolation and stay home until the following three things have happened:

  • You have had no fever (temperature stays less than 100.4 F) for at least 72 hours, i.e. three full days of no fever without the use of medicine that reduces fevers.

AND

  • Other symptoms have improved (for example, cough or shortness of breath have improved)

AND

  • At least 10 days have passed since your symptoms first appeared

Also, please reach out to your medical provider immediately if you experience severe symptoms, including:

  • Worrisome shortness of breath
  • Mental confusion
  • Chest pain or pressure that persists (not just with coughing)
  • Palpitations or irregular heartbeat
  • Fainting or almost fainting

We encourage you to check with your local department of health before discontinuing isolation to make sure our guidance aligns with your local regulations.

If you have not had symptoms, we recommend you:

  • Continue self-isolation and stay home for 10 days from the day you were tested
  • Wear a mask in public and stay 6 feet away from people for the following 3 days after isolation ends
  • If you develop symptoms within that time, isolate using the symptomatic instructions above

"Not Detected" Result means no SARS-CoV-2 genetic material was detected.

This is generally good news. Still, we strongly recommend continuing to care for yourself and practicing social distancing and handwashing regardless, as this test can sometimes miss SARS-CoV-2, especially if you haven’t had symptoms, or if you had symptoms but they started more than 7 days before the date of your test.

If you haven’t had any symptoms but you had an exposure to someone who tested positive for COVID-19, we advise you to stay home for 14 days since your last exposure to COVID-19.. If you did not have an exposure to someone who tested positive for COVID-19, we recommend continuing to monitor your health and practice social distancing.

If you are or have been symptomatic, we recommend you continue self-isolation and stay home until the following three things have happened:

  • You have had no fever for at least 72 hours (that is three full days of no fever without the use of medicine that reduces fevers)

AND

  • Other symptoms have improved (for example, when your cough or shortness of breath have improved)

AND

  • At least 10 days have passed since your symptoms first appeared

We understand that keeping up with the seemingly endless coronavirus news can feel overwhelming, so we have created a library of COVID-19 reference materials that are updated daily with the latest on what you need to know and what precautions can be taken to stay healthy.

COVID-19 IgG Antibody Testing

This test identifies a type of antibody present in your system and can indicate that you have mounted an immune response to SARS-CoV-2, the virus that causes COVID-19 (coronavirus) infection.

If your test for COVID-19 antibodies is positive:

This result indicates that your body has likely produced an immune response to COVID-19. Scientists do not yet understand whether having COVID-19 antibodies means that you are protected, and until there is more data it is important to consider yourself at risk should you be exposed again. We also recommend you continue to abide by any municipal orders to shelter-in-place.

If your test for COVID-19 IgG antibodies is negative:

This result indicates that no antibodies to the virus were detected. This can be for a number of reasons, including:

  • Lack of exposure to the virus
  • Testing too early after exposure or infection (less than 14 days from symptom onset, or potential exposure)
  • An insufficient immune response due to conditions or treatments that suppress the immune system
  • Rarely, that you were exposed and this is a “false negative”

With no identified antibodies in your system at this time, it is important to consider yourself at risk for infection should you be exposed. It is also very important to use social distancing practices that are recommended at this time, and to abide by any municipal orders to reduce transmission.

If your test for COVID-19 IgG antibodies is equivocal:

This indicates that your result could not be determined to be either positive or negative. This may be due to the timing of the test relative to your symptoms or exposure, or could represent the presence of an immune response to other types of coronaviruses like those that cause the common cold. Depending on your specific clinical situation, you may want to repeat the test in 5-7 days. We recommend connecting with your healthcare provider to discuss further.

We understand that keeping up with the seemingly endless coronavirus news can feel overwhelming, so we have created a library of COVID-19 reference materials that are updated daily with the latest on what you need to know and what precautions can be taken to stay healthy.

Cholesterol (Lipid) Panel

"Cholesterol" refers to a class of fats, also known as lipids, that circulate through the blood. Cholesterol levels are important as they can affect a person's risk for developing cardiovascular disease.

There are several types of cholesterol that make up the cholesterol/lipid panel:

  • Total cholesterol is a measurement of all of the types of cholesterol in your blood, including HDL, LDL, and triglycerides.
  • Triglycerides are a type of fat that the body generates when excess calories are consumed, particularly calories from carbohydrates and fats. They are stored in fat cells and can circulate in the blood. High levels are associated with increased risk for developing cardiovascular disease and are also often found together with elevated blood sugar. Diet, exercise, and genetics have a major impact on triglyceride levels. When elevated, they can be lowered significantly with improved diet and exercise. (See the recommendations outlined below.)
  • High density lipoprotein (HDL) is considered the "good" cholesterol because it helps the body clear "bad" cholesterol from your arteries and can help protect against heart disease (ie heart attacks and strokes).
  • Low density lipoprotein (LDL) is considered the "bad" cholesterol because it can embed itself in blood vessel walls leading to damage (“atherosclerosis”) and subsequent heart disease (heart attacks and strokes, e.g.).

Interpreting your lipid panel:

  • With a few exceptions, the normal ranges for cholesterol as listed on lab reports can be misleading. Instead, what is normal or abnormal is determined by your overall individualized cardiovascular risk.
  • The primary factors for interpreting an individual’s risk include age, sex, smoking history, blood pressure, family history, and the presence or absence of diabetes.
  • Your provider will reach out to you if they have any additional recommendations regarding your cholesterol results. And if you have questions, don’t hesitate to message us!

Hemoglobin A1C and Glucose Tests

*The explanations below are for non-diabetic individuals.*

Serum Glucose: This lab looks at your blood sugar level at the time of testing.

  • < 100 mg/dL: This is normal.
  • 100-199 mg/dL:
    • If you ate eight hours or less before your blood was taken you were not fasting and this range is normal.
    • If you hadn’t eaten for 8 hours or more you were fasting. Blood sugar levels between 100 and126 mg/dL carry some risk risk for developing diabetes. If you were fasting and your result is 126 mg/dL or greater, you may have diabetes and a follow up test is required to confirm this diagnosis.
  • 200 mg/dL or greater: Whether fasting or not, this level also suggests the diagnosis of diabetes.

Hemoglobin A1c: This is a measure of your average blood sugar level over the past three months. This test result isn’t affected by fasting.

  • <5.7%: This is normal.
  • 5.7-6.4%: This range is associated with an increased risk of developing diabetes
  • >6.4%: This result suggests a diagnosis of diabetes and a repeated test is required to confirm this diagnosis.

Healthy Lifestyle Recommendations:

Here is what One Medical recommends to help avoid and treat heart disease and diabetes. It’s simpler than you might think!

  • Don’t smoke tobacco products.
  • Avoid highly processed and refined foods. A good rule of thumb is if a food label has more than 5 ingredients, it is likely highly processed.
  • Follow a healthy diet by focusing on fresh, multicolored whole foods, fiber (vegetables, whole grains, legumes) and cooking with olive oil. If you can eat mindfully, not too much, and avoid late-night snacks, even better!
  • Treat a food as dessert if it includes any form of sugar in the first few ingredients (this includes sugar, high fructose corn syrup, evaporated cane juice, agave, and honey).
  • Aim for at least 30 minutes of aerobic exercise five or more times a week. And if you feel like you can’t do that, know that any increase in your level of physical activity is good for your heart and aim for whatever you can achieve.

General Lab Tests

Amylase/lipase: These tests check enzymes related to pancreatic function.

Basic metabolic panel (BMP): This lab checks kidney function, electrolytes, and blood glucose (sugar).

Blood Urea Nitrogen (BUN): This is a test of kidney function.

Celiac Disease Panel: This test may be ordered if there is concern that you have Celiac disease, an autoimmune disease that causes an immune response to gluten. Symptoms of Celiac disease may include diarrhea, bloating, abdominal pain, and anemia. If untreated, long term complications can result. While this test is not used solely to diagnose Celiac, it is a good initial step in evaluation.

Cholesterol (lipid panel): This tests for various components of the cholesterol profile. Total cholesterol reflects all portions of the profile added together. There are many considerations in potential treatment for LDL cholesterol values based on individual patient risk factors. HDL reflects “good” cholesterol levels, and higher is generally better for this form of cholesterol. Triglycerides are a component of cholesterol involved in blood sugar and fat storage in the liver. Diet, exercise, and genetics have a major impact on these levels. High triglycerides contribute to an increased risk of heart attack, stroke, and other health problems. Frequently, one or more components of the cholesterol panel are flagged as abnormal when they are, in fact, completely normal based on an individual patient’s risk. Unless you’ve been told otherwise, rest assured a bolded result is not necessarily concerning.

There are many ways to manage your cholesterol levels:

  • Make natural or minimally processed foods the basis of your diet.
  • Fill half of your plate with fruits and vegetables at every meal.
  • Try a Mediterranean diet with a heavy focus on fiber (vegetables, whole grains, legumes) and cooking with olive oil.
  • Treat food as dessert if it includes any form of sugar in the first few ingredients (this includes sugar, high fructose corn syrup, organic evaporated cane juice, agave nectar, and honey).
  • Eat healthy fats like olive oil, fatty fish, avocado, nuts, seeds, and grass-fed meat and dairy. Avoid hydrogenated trans fat.
  • Avoid tobacco use.
  • Get aerobic exercise for at least 20 to 30 minutes three times a week or more.

Complete blood count (CBC): This lab checks for signs of infection or anemia, and looks at various component of blood (red cells, white cells, platelets, etc.) to detect blood-related abnormalities.

Complete metabolic panel (CMP): This lab checks your blood glucose (sugar), electrolyte levels and liver and kidney function.

Creatinine (Cr): This is a test of kidney function.

Fecal Occult Blood test (FOB): In this test, your stool sample is examined for small amounts of blood that may not be visible by simple visual examination. The presence of blood in stool would warrant further investigation for a cause (such as polyps or colon cancer), while the absence of blood would be a reassuring sign. This test can be performed annually as a colon cancer screening tool.

Ferritin: Ferritin is the cellular storage protein for iron. This test is commonly ordered to further evaluate iron levels and potential for iron deficiency. There are many other reasons why ferritin may be ordered, but these are less common. Ferritin can also be a nonspecific marker of inflammation.

Free thyroxine (Free T4): This test is used to evaluate thyroid function and is often checked if TSH results are abnormal as part of a thyroid cascade.

Glucose: This lab looks at your blood sugar. If this level is marked as high or bolded on your form but you were not fasting at the time of your blood draw, it may not actually be abnormal. The normal range applies to fasting samples only.

H. pylori: This test looks for chemical signs of H. pylori in your breath. H. pylori is a bacteria that commonly causes stomach and small intestinal ulcers and is associated with more severe acid reflux (GERD).

Hemoglobin A1c: This is a measure of average blood sugar levels over the past three months. It is a helpful test in screening for and monitoring diabetes. Elevated levels can suggest either a risk for diabetes, or can be used for diagnosis of diabetes, depending on how high the value is.

Hepatic Function Panel: This test evaluates various liver function tests and enzyme levels. Abnormalities can suggest inflammation in the liver or other potential liver or biliary (gallbladder, etc.) related issues.

INR, Prothrombin time: These tests assess blood clotting abilities and are commonly checked for patients who take blood thinners (e.g., Coumadin). It is commonly checked as part of a presurgical evaluation.

Iron (Iron and TIBC): This test looks at your iron levels and iron binding in red blood cells. This test can be helpful in identifying an iron deficiency or overload. It may be ordered if your provider thinks you are anemic, as iron deficiency is one possible cause of anemia. Low levels may be due to some chronic diseases, poor dietary intake, gastrointestinal tract malabsorption, or increased iron needs during times like pregnancy. High levels, on the other hand, may be due to frequent blood transfusions, lead poisoning, liver or kidney disease, or a genetic condition called hemochromatosis.

Magnesium: This test looks at magnesium levels. Magnesium is a mineral and, when deficient in it, you could experience weakness, twitching, cramping, confusion, cardiac arrhythmias, and seizures. You may have this level checked if you are presenting with any of those symptoms, or if you have altered absorption of magnesium in your gastrointestinal tract, or abnormal excretion via your kidneys.

Calcium: This test measures the amount of calcium in your blood. It’s a mineral in the body that is necessary for your body’s nerve, heart, and muscle function. Calcium is also important for bone maintenance and formation, in addition to blood clotting. You may have this checked to monitor any of the systems above, or screen for issues with malabsorption, thyroid disorders, or parathyroid disorders.

Potassium: This tests for levels of potassium electrolytes in your bloodstream. It is commonly monitored in relation to treatment for high blood pressure, but it may also be tested for other reasons.

Prostate specific antigen (PSA): This is a prostate test that can be used to aid in the diagnosis of prostate enlargement, prostate cancer, and other prostate-related conditions.

Serum HCG: This is a blood test that is most commonly used to check for pregnancy and can also approximate how far along in pregnancy someone is (if the test is positive). This test may be checked for reasons unrelated to pregnancy, as various conditions can potentially elevate HCG levels.

Thyroid Stimulating Hormone (TSH): This test is used to evaluate thyroid function and is useful in diagnosing or managing thyroid disorders including hyperthyroidism or hypothyroidism.

Triiodothyronine (T3): This test is used to evaluate thyroid function and is often checked if TSH results are abnormal as part of a thyroid cascade.

Uric acid: This test is most commonly used to aid in the diagnosis or management of gout. There are other reasons why this test may be ordered, but these conditions are uncommon.

Urinalysis (UA): This test evaluates a urine sample for signs of infection, blood, or other abnormalities.

Urine culture: This test looks for bacterial growth in urine. It can be helpful in determining if you have a urinary tract infection. If abnormal, sensitivity testing is typically performed to determine which antibiotics would be effective against the bacteria isolated in the urine sample.

Urine Microalbumin: This urine test is used to evaluate kidney function and is routinely monitored for patients with high blood pressure and diabetes, among other conditions.

Antibody/immunity tests

Hep A Ab, Total: Hepatitis A is a viral infection of the liver. This tests for the presence of hepatitis A antibodies. Elevated levels reflect immunity either through previous vaccination or exposure to the illness.

Hep B Ab, Total: Hepatitis B is a viral infection of the liver. This tests for the presence of hepatitis B antibodies. Elevated levels reflect immunity either through previous vaccination or exposure to the illness.

Measles, Mumps, Rubella (MMR) Immunity Profile: This lab test indicates if you have immunity to measles, mumps, and rubella. If you are deemed to not be immune, you will often be offered vaccination. This may be used when you are not aware of your last MMR vaccination, for proof of vaccination, or during a travel examination visit in the setting of uncertain vaccination status.

Varicella Zoster Virus (VZV) Antibodies, IgG: This test is useful in determining if you are immune to varicella zoster infection. You should note that this test cannot distinguish between prior infection causing immunity and current infection, and some people who have been vaccinated will not have a positive IgG result.

Inflammatory/Autoimmune tests

Antinuclear Antibody Panel (ANA): This test looks for specific antibodies that may be useful in diagnosing various autoimmune conditions.

C-reactive protein (CRP): This test assesses levels of an inflammatory marker that can be elevated in various situations, including infectious, autoimmune, and rheumatologic conditions.

Erythrocyte Sedimentation Rate (ESR): This test assesses levels of an inflammatory marker that can be elevated in various situations, including infectious, autoimmune, and rheumatologic conditions.

hs-CRP: This test assesses levels of an inflammatory marker that can be helpful in assessing risk for heart disease.

Rheumatoid Factor (RF): This test looks for specific antibodies that may be useful in diagnosing various autoimmune conditions.

Vitamin tests

B12: This test checks for your levels of vitamin B12, which is supplied by animal products (including meat, fish, milk products, and eggs) in the diet, as well as in supplements, fortified foods, and some nutritional yeasts. Deficiency may be due to low intake of vitamin B12 from your diet or poor absorption of B12 in your GI tract. Since B12 is needed for proper nervous system and brain function and red blood cell formation and deficiency may lead to anemia, a deficiency should be identified and corrected by dietary changes and supplementation if needed.

Folate: This test checks for folate levels. Folate, or folic acid, is a B vitamin needed for red blood cell production and DNA production and repair. Dietary contributions of folate are found in citrus fruit and dark greens, among other foods. Deficiency may be due to poor dietary intake or absorption, or due to certain diseases or genetic mutations.

Vitamin D: This tests for levels of vitamin D, a vitamin that is found in some foods and also produced through sunlight exposure. This is frequently checked to evaluate for fatigue or depressed mood and is associated with calcium absorption and bone health.

Infectious disease/STI tests

Chlamydia: This test is used to detect the presence of chlamydia, a sexually transmitted disease, in the urine, throat, rectum, urethra, or cervix. This is commonly tested in combination with gonorrhea, and the two are generally reported together (i.e. Ct/GC NAA).

Gonorrhea: This test is used to detect the presence of gonorrhea, a sexually transmitted disease, in the urine, throat, rectum, urethra, or cervix. This is commonly tested in combination with chlamydia, and the two are generally reported together (i.e. Ct/GC NAA).

Hep C: Hepatitis C is a viral infection of the liver. This tests for the presence of hepatitis C antibodies, which can be associated with active hepatitis C infection.

HIV (HIV Screen 4th Generation wRfx): This test is used to screen for the presence of HIV antibodies and an HIV specific antigen (molecular marker of HIV). A positive test automatically reflexes to additional confirmatory testing for diagnosis.

Lyme Disease Ab: This is an antibody test that is used to aid in diagnosis of Lyme disease, a tick-borne illness, spread through the bite of an infected tick. It may be useful in seeing if symptoms, such as a bullseye rash, fatigue, and body aches, are due to a Lyme infection.

Mono (Mono Qual W/Rflx Qn): This tests for antibodies associated with mononucleosis (mono) and can aid in the diagnosis of acute or active infection.

Quantiferon Gold or Tb test: This test is used to identify Mycobacterium tuberculosis, the bacteria that causes tuberculosis. Tuberculosis is an infectious disease that is spread through the air and can cause symptoms like night sweats, weight loss, and cough. This test might be used for patients with previous exposure to TB, high risk individuals, or those who received the BCG vaccine in childhood (this is not generally part of childhood vaccination in the United States and is more common among individuals born outside of the US).

Rapid plasma reagin (RPR): This test is used to screen for syphilis infection and monitor effectiveness of syphilis treatment.

Vaginitis: This test examines vaginal fluid for abnormal bacteria, yeast, or other organisms.

Cultures

Stool cultures: Stool cultures examine a stool sample for the presence of bacteria, usually Campylobacter species, Salmonella species, and Shigella species. This may be done if you have had symptoms such as diarrhea, fever, and abdominal pain and cramping.

Strep: This test is performed to aid in diagnosis of strep throat. This throat swab is cultured for bacteria Streptococcus pyogenes, also known as group A streptococcus, the most common cause of bacterial infections of the throat.

Wound Cultures: This test checks a wound for sources of infection (fungus, bacteria). This can be used to determine the correct course of treatment, if one is needed. It can also be used after treatment to determine if the treatment was effective.

Hormone tests

Cortisol: This test looks at cortisol levels. Cortisol is a steroid hormone produced by the adrenal glands and associated with many processes in the body. It is a major contributor to the “fight or flight” response, helping to release large amounts of energy and strength in short bursts. Excessively high or low cortisol levels can be associated with a number of potential endocrine disorders.

Cortisol: This test looks at cortisol levels. Cortisol is a steroid hormone produced by the adrenal glands and associated with many processes in the body. It is a major contributor to the “fight or flight” response, helping to release large amounts of energy and strength in short bursts. Excessively high or low cortisol levels can be associated with a number of potential endocrine disorders.

Estradiol: This test looks at estrogen levels, the primary female sex hormone. However, men also have estrogen (though at lower levels). This hormone impacts female sex characteristics, menstruation, reproductive health, fertility, and bone and joint health.

Follicle stimulating hormone (FSH): This test looks at follicle stimulating hormone levels. In women, this hormone impacts the menstrual cycle and egg production, and varies depending on timing of a woman’s menstrual cycle. Levels in males impact sperm production.

Luteinizing hormone (LH): This test looks at levels of luteinizing hormone, a hormone that impacts ovulation in women and testosterone production in males.

Prolactin: This test looks at levels of prolactin, a hormone produced in the pituitary gland. This test can be used to evaluate possible issues with the pituitary gland and hypothalamus. It may be used to evaluate fertility, erectile dysfunction, abnormal hair growth, headaches, visual impairment, painful intercourse, or abnormal milk production outside of breastfeeding.

Testosterone: This test looks at testosterone levels, a sex hormone that is important for both men and women. This hormone impacts sex drive, reproductive health, fertility, and physical characteristics.

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The One Medical blog is published by One Medical, an innovative primary care practice with offices in Boston, Chicago, Los Angeles, New York, Phoenix, Portland, the San Francisco Bay Area, Seattle, and Washington, DC.

Any general advice posted on our blog, website, or app is for informational purposes only and is not intended to replace or substitute for any medical or other advice. The One Medical Group entities and 1Life Healthcare, Inc. make no representations or warranties and expressly disclaim any and all liability concerning any treatment, action by, or effect on any person following the general information offered or provided within or through the blog, website, or app. If you have specific concerns or a situation arises in which you require medical advice, you should consult with an appropriately trained and qualified medical services provider.